Furnace construction



March 1942- J. w. .THRO'CKMORTON ETAL 2,276,529

FURNACE CONSTRUCTION Filed July 9, 1941 2 Sheets-Sheet 2 ATTORNEY,

Patented Mar. 17, 1942 FURNACE CONSTRUCTION John w. Throckmorton, Wilton, and John s. Wallis, Darien, Conn., assignors to Petra-Chem Developmen Company, New York, N. Y., a cornotation of elaware Application July 9, 1941, Serial-No. 401.594

5 Claims.

This invention relates to improvements in furnace construction and refers more particularly to a vertical tube furnace substantially circular in cross section, in which the heating elements or tubes are arranged in concentric circles around the interior wall surface of the furnace, the outer tube bank or circle of tubes adjacent or in close proximity to the wall having extended surfaces or fins arranged to support the insulating or refractory material constituting the interiorof the furnace and exposing increased heat absorption surfaces; the inner circle of tubes'constituting the inner tube bank and receiving the main heating duty, serving to partially shield th outer bank from excessive radiant heat.

In order to more uniformly distribute the heat along the surfaces of the inner bank, it is contemplated that extended surfaces or fins may be used in the convection section of the furnace and bare or plain surfaced tubes in the radiant section.

Heating gases are supplied'to the furnace by A line L5 in Fig. 4.

properly positioned burners arranged to distribute the heat uniformly within-the furnace. In the upper part of the furnace is positioned a cone for reflecting the radiant heat toward the tubes in the radiant section and deflecting the gases to fiow over the tube surfaces in the convection section or cooler portion of the furnace.

An advantage of the design lies in its simplicity and efiiciency, the cost of construction being reduced by the manner in which the tubes are sup ported and the reduction in the amount of structural steel necessary to support the furnace walls.

A further object of the invention is to make a furnace-boiler or economizer using various combinations of 'bare' and fin tubes, while maintaining at all times a. light weight furnace setting or enclosing wall structure.

By means of this design, itis possible to have a completely prefabricated, shop assembled furnace with the setting, wall structure and heating elements r light weight construction.

In design, the course of thegas flow and arrangement of heat exchange elements is such that an optimum condition is provided for the Fig. 1 is a vertical section of one type of fur-.

nace design according to the invention.

Fig. 2 is a horizontal section taken along .th

line 2-2 in Fig. 1.

Fig. 3 is a horizontal section taken alongthe line 3-3 in Fig. 1. a v

Fig. 4 is aslightly modified type of construction in which the wallinsulation is reduced somewhat in the convection section.

Fig. 5 is a fragmentary view taken along the.

Fig. 6 is a fragmentary view taken along the line 6-45 in Fig. 4. i

Fig. 7 is a modified design taken along the line il in Fig. 8 and showing the invention as applied to an economizer installed in the flue gas passageway or breeching.

Fig. 8 is a sectional view taken along the line 8-8 in Fig. 7.

Referring to the drawings, on a base i and supporting the furnace from below are pedestals 2., Upon the pedestals is a steel plate furnace casing, comprising a bottom 3, side wall 3 and a top 5;. Within the casing 4 and supported from the top by means of a channel 5 are banks of heating tubes arranged in concentric circles around the inner surface of the furnace. Surrounded by thefurnace casing is a wall of insulating or refractory material shown at l. The outer circle or bank of tubes 8 have fins or extended surfaces 9, shaped to conform with the inner cylindrical surface of the insulatingor refractory material, both the tubes and the fins serving to support the insulating or refractory material from within, the outer casing 4 supporting the insulating or refractory material on the outside. The inner circle of tubes or inner tube bank II] are plain surfaced tubes within the radiant section or that portion of the furnace subjected to radiant heat, while the upper portions of the tubes l0 within the convection section of the furnace or that portion receiving principally convection heat have extended surfaces or fins ll extending radially from the vsurface of the tubes. The particular type of fins or extended surfaces utilized is of no importance, theadvantages contemplated being the use of the fins on the outer bank to support the insulating or refractory wall and the fins on the inner bank offering increased absorption surface for the inner bank of tu-besin the convection section where the combustion gases are at reduced temperature. The vertical tubes 8 and I 0 are equipped with a conventional type of return bends and removable plugs 12 at top and bottom, to facilitate cleaning.

port 13 upon which the inner flange of the channel 6 rests. This support I3 also carries the hangers M which support the deflecting cone l5. On top of the furnace setting is a chimney or flue i6. Extending through apertures in the refractory material, forming the bottom of the furnace are burners I'l located to distribute the heating gases uniformly throughout the combustion space. v

The passage of the heating gases is shown by the arrows in Fig. 1, Fig. 4 and Fig. '7. In Figs. 1 and 2 the gases pass upwardly through the radiant section, either in a linear flow or in a spiral course according to the angle at which the burners are positioned.

In the lower portion of the furnace where the firing takes place, the exposed surfaces of the tubes are subjected principally to radiant heat. The inner circle or inner bank of tubes are preferably staggered with the outer bank, thereby distributing the radiant heat more uniformly over the exposed surfaces of the separate tube banks. A sufficiently high heat transfer rate is obtained in this zone to warrant the exposure of plain tubes for the inner tube bank, while fins or extended surfaces are used in the outer bank, due to the fact that the outside half of the tube surfaces is embedded and insulated from the heat in the insulating material. gested, the extended surface elements, or fins, on

I the outer bank not onlyoffer increased heat absorption surfaces but also support the insulating or refractory material which forms the inner wall of the furnace. In its passage upward through the furnace, the gas is diverted near the upper portion of the radiant section .by the cone l5. This inverted cone has a cylindrical upper portion which forms a restricted annular space or channel, between the outer periphery of the cylindrical portion of the cone and the furnace wall. The combustion gas, diverted by the cone, flows through this restricted channel or annular passageway in its travel from the radiant section of the furnace to the fiue l6. This restricted channel or annular passageway is, for convenience, designated as the convection section of the furnace as the portions of the tubes positioned therein receive principally convection heat. This convection section is distinguished from that portion of the furnace below the cone i5, designated as the radiant section, wherein the tubes receive principally radiant heat.

Although not indicated in the drawings, sections of the top part of the furnace casings 5 are removable in order that plugs l2 may be removed from the tubes for cleaning or the vertical tubes of either bank taken from the furnace in case replacement or repair is necessary.

In the modification shown in Fig. 4, the convection section is surrounded by insulating or refractory material of considerably less thickness than that surrounding the radiant section. This is feasible as the temperature of the heat ex- As previously sugof the furnace, a supplementary cylindrical sheet l8, conforming in shape with the inner surface of the furnace, may be required to hold the insulating or refrac ry material in this section of the furnace in pla e. The economizer shown in Figs. 7 and 8, preferably interposed in the furnace flue or passageway through which heating gases are discharged, adopts the principal features of the vertical tube furnace shown in Figs. 1 and 4. This structure includes a base i, upon which stand pedestals 2. The pedestals support the base plate 3 and enclosing sides of the metallic casing 4. The heat exchange elements in the economizer have a plurality of vertical tubes including a wall bank 19 and internally positioned tubes 20. The wall bank I! is partially embedded in the insulating or refractory material 1 and, to-. gether with the fins or extended surfaces 9, support the insulating or refractory wall between the tubes and the casing 4. The lower and upper ends of the tubes may be connected by means of return bends 2|, as shown in Fig. 7 or by headers of any suitable type, in order to obtain the desired fluid flow therethrough. The inlet and outlet connections to the tube bank will be arranged according to the desired method of flowing the fluid through the tubes. These connections have been purposely omitted from the drawings in the interests of simplicity, as the method of coursing the fluids through the tubes in either the economizer or the furnace forms no part of the instant invention, except that it is important that the fiuid be distributed in its passage through the tubes in a manner to obtain the most efficient and economical heating.

The flue gas passing through the economizer is admitted through the pipe 22, flows in the direction shown by the arrows through the heating section of the economizer and out through the discharge pipe 23. In the lower and upper portions of the economizer, adjacent the inlet and outlet ports, where the combustion gas travels across the tube surfaces and more nearly at a right angle to the'axes of the tubes, plain or bare surfaced tubes are used. In the mid-section of the economizer or intermediate the inlet and discharge ports where the heating gas flows relatively parallel to the tubes, extended or fin surfaces II are employed. gThis arrangement serves to distribute the heat absorption surface more uniformly through the'length of the tubes, while the fins on the tube bank adjacent the insulating or refractory wall serve not only as a support but also add a heat absorption surface which is lostto the tubes by partially embedding them in the wall of the economizer.

- Over the upper ends of the tubes is a removable cover 24 which may be taken offfor cleaning, replacement, or repair of the tubes. In the inlet pipe 22 may be positioned a burner 25 to augment the heat of the gases passing through change fluid or combustion gas passing over the the economizer.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of our claims. It is further obvious that various changes may be made in details within the scope of our claims without departing from the spirit of our invention. It is, therefore, to be understood that our invention is not to be limited to the specific details shown and described.

Having thus described our invention, we claim:

- surfaces in the radiant section and extended 2. A furnace construction of the character v ing increased heat absorption surface, an inner tube bank assuming the main heating duty and shielding the outer tube bank from excessive radiant heat, a source of combustion gas within the tube banks and an outlet flue in the top of the furnace.

3. A furnace construction ,of the character described including an enclosing wall structure of insulating or refractory material substantially circular in cross section and having radiant and convection sections, a plurality of banks of vertical tubes arranged adjacentthe inner wall surface in concentric circles, extended surface elements on the outer tube bank in close proximity to the wall supporting the insulating or refractory material and exposingiincreased heat absorption surface, an inner tube bank having plain surfaces in the convection section of the furnace, a source of combustion gas within the tube banks and an outlet flue in the top ofthe furnace.

4. A heater construction of the character described, including an enclosing wall structure of insulating or refractory material, vertical tubes adjacent the-insulating or refractory walls and partially embedded therein, extended surface elements on the wall tubes assisting the wall tubes insupporting the insulating or refractory mate-v rial, a bank of vertical tubes within the wall tube bank, a depending deflector member having a lower conical portion forming. a convection zone, extended surface elements on the inner tube bank exposing increased heat absorption surfaces in said convection zone, a combustion gas ,supply, an inlet for introducting said gas to the heater, and an outlet for discharging spent gas therefrom.

5. A furnace construction of the character described including an enclosing wall structure of insulating or refractory material having radiant and convection sections, two banks of vertical tubes arranged adjacent the inner wall surface in concentric banks, extended surface'elements on the outer tube bank in close proximity to the wall supporting the insulating or refractory material and exposing increased heat absorption surface, an inner tube bank assuming the main heating duty and shielding the outer tube bank from excessive radiant heat, extended "surface on the inner tube bank in the convection zone, a source of-combustiorr gas within the tube banks and an outlet flue in the top of the furnace JOHN W. THROCKMORTON. JOHN S. WALLIS. 

